In insulation polymers, there exist rich dielectric phenomena ranging from the shape change and reorientation associated with polar polymer chains and bonds, to mesoscopically charged giant dipoles, and pure electrostatic interaction at the meso- and macroscopic levels. Many of these phenomena can be used to develop high performance field activated electroactive polymers (FEAPs) exhibiting very large strain and elastic energy density, characteristics that are very attractive for sensors and actuators.
FEAPs are a class of insulating materials in which response to an electric field is a mechanical strain which can originate from the dipolar response under, and the Columbic interaction with, external electric signals. There are many polarization mechanisms in insulating polymers, from the molecular to the mesoscopic, and even the macroscopic level. These mechanisms couple strongly using mechanical deformation and can be used to create electromechanical polymers, which can be used to develop high performance actuators and sensors. FEAPs feature fast response speed, limited by the polymer dielectric and elastic relaxation times, very large strain level (to more than 100% strain), high electromechanical efficiencies, the ability to operate at the micro/nano-electromechanical levels and a highly reproducible strain response under electric fields. A piezopolymer with 50% energy conversion efficiency will bring breakthroughs in energy harvesting technology, as well as to sensor and actuator technologies.
Applications for FEAPs include pressure/stress sensors in microphones and automobile/highway condition monitoring, loudspeakers in audiosystems, sonar transducers for underwater navigation, ultrasonic transducers for medical diagnosis/imaging, actuators for moving parts, and nondestructive evaluation and monitoring of various civil, mechanical, and aerospace systems. FEAPs exhibit many characteristics favorable to electromechanical actuators and sensors, such as high flexibility, light weight, high stress impact resistance, and easy manufacturing. In the past fifteen years, several discoveries and developments have led to great improvements in the electromechanical performance of field activated electroactive polymers.